Rb26 Head-shims Vs Shimless Buckets

[20SIX]

Hey guys.

Looking to hear about experiences good/bad with running shimless buckets, ideally in a worked head.

Possibly looking at going down this road, getting mixed opinions though.

My situation: running 1mm oversized ss valves, 272 cams with a decent lift ( head relieved ) springs, ported etc. was running standard buckets, shimmed.

Ended up having a shim pop out of place, very lucky nothing touched, no damage..

Looking at running shimless buckets and having it all setup to do so.

Would like to hear feedback from anyone who has done so and what they think. Reliability, wear, maintenance ..

Thanks

[Ben C34]

The only way a shim can come out is with uncontrolled Valvr motion, ie float. Which is bad. Fix that and shims stay in.

[Leroy Peterson]

very lucky.

who installed/measured the shims?

some people like to cut up feeler gauges and put them under existing shims rather than ordering new ones... just a thought.

[GTRPSI]

When saying shimless, you actually mean the thicker buckets as you still need to shim them anyway to achieve the correct valve clearance.

Its to do with the base circle of the cam, if its smaller than stock you need thicker shims, or use the thicker lifter with thinner shims.

Now having said that, most shims that ive seen spat out where when smaller base circle cams were used with standard buckets and thicker shims.

For some reason the thinner shims used with thicker buckets stay in place better than the thicker shims with stock buckets......

Yes valve float is the enemy.

[scotty nm35]

Some VQ's run shimless Peter, you need to order a different bucket if the clearance is out. Sounds like hard work to me.

[GTSBoy]

Yes, proper shimless buckets can become expensive when coupled with aggressive cams (which is of course one of the main reasons for wanting shimless buckets anyway!) because clearance changes (wear) will become more frequent and you can't just ignore it. Have to buy some new buckets each time you have to adjust anything. If you suffer any valve seat recession at all you will come to hate it also (same reason).

[GTRPSI]

Some VQ's run shimless Peter, you need to order a different bucket if the clearance is out. Sounds like hard work to me.

That would be a absolute total pain in the arse.

RB26 run with shims without issues when staying around factory shim thicknesses.

Our current setup is 280 degree 11.5mm lift cams with thicker buckets but with stock thickness shims, the only reason i went for the thicker buckets was because of the thicker shim issues.

Another head near my place was assembled with the same spec cams and same bucket/shim setup for a 28 thats turning over 9000Rpm ATM without shims falling out.

Both us use new double valve springs with seat preload and lift tension checked and adjusted with shims also under the valve springs, something which most workshops dont check and adjust.

That can make of break your valve bounce issues......never assume that the seat pressure is correct even when using new springs, all you need is a valve that sits a little deeper and you know whats going to happen.....always put a little more spring preload in because they will go soft with high lift cams and heat cycles, not too much because you dont want to chew out your nice new cams.

Edited October 21, 2015 by GTRPSI